Index: src/org/python/core/PySystemState.java
===================================================================
--- src/org/python/core/PySystemState.java	(revision 3414)
+++ src/org/python/core/PySystemState.java	(working copy)
@@ -576,7 +576,7 @@ public class PySystemState extends PyObj
     }
 
     private static Hashtable builtinNames;
-    public static String[] builtin_module_names = null;
+    public static PyTuple builtin_module_names = null;
 
     private static void addBuiltin(String name) {
         String classname;
@@ -615,10 +615,12 @@ public class PySystemState extends PyObj
             addBuiltin(tok.nextToken());
 
         int n = builtinNames.size();
-        builtin_module_names = new String[n];
+        PyObject [] built_mod = new PyObject[n];        
         Enumeration keys = builtinNames.keys();
         for (int i=0; i<n; i++)
-            builtin_module_names[i] = (String)keys.nextElement();
+        	built_mod[i] = Py.newString((String)keys.nextElement());
+        
+        builtin_module_names = new PyTuple(built_mod);
     }
 
     static String getBuiltin(String name) {
Index: Lib/test/test_sys.py
===================================================================
--- Lib/test/test_sys.py	(revision 3414)
+++ Lib/test/test_sys.py	(working copy)
@@ -232,10 +232,7 @@ class SysModuleTest(unittest.TestCase):
             self.assert_(isinstance(sys.api_version, int))
         self.assert_(isinstance(sys.argv, list))
         self.assert_(sys.byteorder in ("little", "big"))
-# Jython transition 2.3
-# sys.builtin_module_names is missing.
-# http://jython.org/bugs/1768984
-#        self.assert_(isinstance(sys.builtin_module_names, tuple))
+        self.assert_(isinstance(sys.builtin_module_names, tuple))
         self.assert_(isinstance(sys.copyright, basestring))
         self.assert_(isinstance(sys.exec_prefix, basestring))
         if test.test_support.is_jython: